1. Field of the Invention
The present invention relates to a hammer used in breaking polycrystalline silicon, which is used as a material for semiconductor-grade silicon, into appropriately sized pieces.
2. Background Art
Materials for wafers of single crystal silicon for semiconductors include, for example, polycrystalline silicon of extremely high purity greater than 99.999999999%. Single crystal silicon is produced by melting polycrystalline silicon of high purity in a crucible to grow single crystal silicon with a seed crystal of single crystal silicon. In the case of manufacturing single crystal silicon, the purity of lumps of polycrystalline silicon used as a material is critically important. Since single crystal silicon is contaminated with impurities during manufacturing processes to result in a large deterioration in the quality of single crystal silicon, it is necessary to prevent the contamination of polycrystalline silicon with the impurities as much as possible.
In the Siemens method, polycrystalline silicon of high purity is manufactured by the procedures in which trichlorosilane (SiHCl3) gas and hydrogen gas are supplied to a reaction furnace in which a silicon seed is arranged and high-purity polycrystalline silicon deposits on the silicon seed. According to this method, an ingot of polycrystalline silicon having a diameter of about 140 mm and formed substantially in a columnar shape is obtained.
The ingot of polycrystalline silicon breaks by being struck with a hammer, and thereby lumps of polycrystalline silicon can be obtained. Each of the lumps of polycrystalline silicon is allowed to be put into the crucible. However, where the striking part of the hammer has a low degree of hardness, the striking surface wears and dust resulting from the wear may be mixed into broken pieces of polycrystalline silicon.
For example, Japanese Unexamined Patent Application, First Publication No. H06-218677, and Japanese Unexamined Patent Application, First Publication No. H10-006242 have disclosed a hammer having a striking part made of a hard metal with a high degree of hardness and less likely to wear by striking, as a hammer used for breaking polycrystalline silicon.
Incidentally, in the hammer disclosed in the above Patent Documents, since the striking surface is made to be relatively flat, polycrystalline silicon may be broken into smaller pieces upon striking. Thus, there is a problem that silicon powder is generated in a greater quantity resulting in a low yield of lumps of polycrystalline silicon. Further, an edge formed at the periphery of the striking surface easily chips causing concern that pieces of the striking part may be mixed with broken pieces of polycrystalline silicon.
Further, since a head main body (made of steel, for example), which is connected to a handle portion, and a striking part (made of tungsten carbide) equipped with a striking surface are formed separately from each other, the striking part may be separated from the head main body on impact. Also, since the head main body is made of a material having a lower degree of hardness than the striking part, the surface bonded with the striking part is liable to wear and metal dust resulting from the wear may be mixed into broken pieces of polycrystalline silicon.
The present invention has been made in view of the above circumstances, an object of which is to provide a hammer capable of suppressing the generation of silicon powder upon breaking of polycrystalline silicon and also preventing pieces of a hammer-constituting member from being mixed into broken pieces of polycrystalline silicon.